1. Field of the Invention
The present invention relates to a bicarboxyl monomer, copolymer and their preparing process and, more particularly, to a dispersant suitable for processing a ceramic powder suspension.
2. Description of Related Art
Titanate-based ceramic powders such as barium titanate and lead zirconium titanate powders have been applied in manufacturing various electric devices (e.g. capacitors, inductors, or piezoelectric sensors). For the applications mentioned above, the slurry of titanate-based ceramic materials or powders has to be prepared first. Normally, the slurry is prepared by adding titanate-based ceramic powder (e.g. barium titanate powder) into a solvent. The solvent used for the slurry can be either organic or water-based. Owing to safety, economic, and environmental concerns, the preparation of water-based slurries has currently been preferred.
It is clear that the preparation of a well-dispersed or stable aqueous slurry of ceramic powder is an important issue in the ceramic industry. The dispersibility of ceramic powder in aqueous suspension is well-known to be highly related to the quality of the corresponding sintered products. For example, the barium titanate slurries with poor dispersion cannot form a uniform microstructure, which leads to a lower green packing density and poor electrical properties of the sintered product. In order to obtain good quality of the sintered ceramic products, a dispersant is usually added to the ceramic slurry before further manufacturing process.
For the aqueous titanate-based ceramic slurry, ammonium polymethacrylate, known as Darvan C commercially, is commonly used as a dispersant. Besides, the dispersion of other ceramic particles, e.g. aluminum oxide, zirconium oxide or titanium nitride, in aqueous solution also uses Darvan C as a dispersant. Although the dispersing effectiveness of Darvan C is acceptable, improvement is still required. For example, a high level of leached barium ions is found in barium titanate slurry when Darven C was used as a dispersing agent, which may cause abnormal grain growth and formation of inhomogeneous microstructure. Moreover, the effectiveness of Darvan C toward dispersing barium titanate powder with small particle size, especially in a nanometer level, remains to be examined. Finally, owing to the trend of miniaturization of electronic parts or devices, the traditional processes for the related ceramic slurry need to be modified or even reformed. Meanwhile, the dispersion of ceramic particles in slurries needs to be improved further.
The present invention is to provide a bicarboxyl monomer, copolymer and their preparing process to mitigate and/or solve the aforementioned problems.